Securities - Scheduled Contractual Maturities of AFS (Details) $ in Thousands	Jun. 30, 2025 USD ($)
Amortized cost
Within One Year	$ 341,665
After One Year through Five Years	760,312
After Five Years through Ten Years	738,474
After Ten Years	11,194,807
Total	13,035,258
Fair value
Within One Year	341,871
After One Year through Five Years	730,372
After Five Years through Ten Years	674,471
After Ten Years	10,742,199
Total	$ 12,488,913
Weighted-average yield
Within One Year	2.96%
After One Year through Five Years	1.37%
After Five Years through Ten Years	3.18%
After Ten Years	4.71%
Total	4.38%
U.S. Treasury securities
Amortized cost
Within One Year	$ 164,692
After One Year through Five Years	591,576
After Five Years through Ten Years	0
After Ten Years	0
Total	756,268
Fair value
Within One Year	164,423
After One Year through Five Years	566,639
After Five Years through Ten Years	0
After Ten Years	0
Total	$ 731,062
Weighted-average yield
Within One Year	3.61%
After One Year through Five Years	1.06%
After Five Years through Ten Years	0.00%
After Ten Years	0.00%
Total	1.62%
U.S. government agency and U.S. government-sponsored enterprise debt securities
Amortized cost
Within One Year	$ 16,596
After One Year through Five Years	26,929
After Five Years through Ten Years	201,231
After Ten Years	60,859
Total	305,615
Fair value
Within One Year	16,507
After One Year through Five Years	26,074
After Five Years through Ten Years	176,330
After Ten Years	51,381
Total	$ 270,292
Weighted-average yield
Within One Year	0.93%
After One Year through Five Years	1.36%
After Five Years through Ten Years	2.00%
After Ten Years	1.98%
Total	1.89%
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities
Amortized cost
Within One Year	$ 4,782
After One Year through Five Years	93,119
After Five Years through Ten Years	103,578
After Ten Years	9,785,745
Total	9,987,224
Fair value
Within One Year	4,754
After One Year through Five Years	89,666
After Five Years through Ten Years	94,250
After Ten Years	9,576,240
Total	$ 9,764,910
Weighted-average yield
Within One Year	3.57%
After One Year through Five Years	2.87%
After Five Years through Ten Years	2.89%
After Ten Years	5.06%
Total	5.02%
Municipal securities
Amortized cost
Within One Year	$ 9,118
After One Year through Five Years	23,367
After Five Years through Ten Years	7,108
After Ten Years	245,355
Total	284,948
Fair value
Within One Year	8,992
After One Year through Five Years	22,510
After Five Years through Ten Years	6,695
After Ten Years	201,000
Total	$ 239,197
Weighted-average yield
Within One Year	1.81%
After One Year through Five Years	2.31%
After Five Years through Ten Years	3.56%
After Ten Years	2.23%
Total	2.26%
Non-agency mortgage-backed securities
Amortized cost
Within One Year	$ 11,858
After One Year through Five Years	4,196
After Five Years through Ten Years	3,557
After Ten Years	715,403
Total	735,014
Fair value
Within One Year	11,702
After One Year through Five Years	4,147
After Five Years through Ten Years	3,556
After Ten Years	616,925
Total	$ 636,330
Weighted-average yield
Within One Year	0.47%
After One Year through Five Years	3.11%
After Five Years through Ten Years	5.51%
After Ten Years	2.35%
Total	2.34%
Corporate debt securities
Amortized cost
Within One Year	$ 11,000
After One Year through Five Years	0
After Five Years through Ten Years	328,500
After Ten Years	304,000
Total	643,500
Fair value
Within One Year	10,980
After One Year through Five Years	0
After Five Years through Ten Years	299,389
After Ten Years	224,275
Total	$ 534,644
Weighted-average yield
Within One Year	5.32%
After One Year through Five Years	0.00%
After Five Years through Ten Years	3.38%
After Ten Years	1.97%
Total	2.75%
Foreign government bonds
Amortized cost
Within One Year	$ 123,619
After One Year through Five Years	21,125
After Five Years through Ten Years	50,000
After Ten Years	50,000
Total	244,744
Fair value
Within One Year	124,513
After One Year through Five Years	21,336
After Five Years through Ten Years	49,759
After Ten Years	39,735
Total	$ 235,343
Weighted-average yield
Within One Year	2.46%
After One Year through Five Years	1.95%
After Five Years through Ten Years	4.67%
After Ten Years	1.50%
Total	2.67%
Asset-backed securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	33,445
Total	33,445
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	32,643
Total	$ 32,643
Weighted-average yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	0.00%
After Ten Years	5.03%
Total	5.03%
CLOs
Amortized cost
Within One Year	$ 0
After One Year through Five Years	0
After Five Years through Ten Years	44,500
After Ten Years	0
Total	44,500
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	44,492
After Ten Years	0
Total	$ 44,492
Weighted-average yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	5.73%
After Ten Years	0.00%
Total	5.73%